Pulse driven hydraulic pump

ABSTRACT

An apparatus (3) for pumping fluid from a fluid source (5) to a predetermined location (7) remote from the fluid source. The apparatus (3) comprises an hydraulically operated pump (9) having a fluid pumping chamber and means for storing potential energy. The pump (9) is connected through a control means (19) to the predetermined location (7) upstream and to the source (5) downstream. Control means (19) is also connected to second pumping means (17) and allows spaced pulses of hydraulic pressure to flow from pumping (17) through conduit (15) to pump (9). The hydraulic pulses operate pump (9) to both draw fluid from source (5) into the pumping chamber and to store a portion of the pulse energy. In the period between pulses the stored energy is used to drive pump (9) to supply the drawn fluid to predetermined location (7) and to return a volume of hydraulic fluid equal to that of the actuating hydraulic pulse. Pump (9) may be either twin diaphragm or twin piston type, coupled in tandem; examples of both types are disclosed.

The present invention relates to a pump for pumping fluids, and anapparatus which may incorporate the pump, for pumping fluids from areservoir to a predetermined location. In particular, the presentinvention relates to a pump and an apparatus for pumping water.

Generally a water pump functions by performing two operations eitheralternately or simultaneously. First, the water to be pumped is drawnfrom a water source into the water pump, and second, the water isexpelled from the water pump by way of a conduit to a desired location.

With regard to the first operation, in view of atmospheric pressure andfrictional resistance considerations, it is necessary to locate the pumpin close proximity to the water source. As a consequence, the energy toactuate the pump has to be brought to the pump at the water source.Traditionally, this has been accomplished in the following ways:

1. Electricity is carried to the water pump, either on poles orunderground. The disadvantage with this arrangement is that in manyinstances the water pump is remote from existing power lines and thuspower lines have to be laid to the water pump. This is both inconvenientand expensive.

2. A petrol or diesel engine is positioned adjacent the water pump andthe water source. The disadvantage with this arrangement is that,although the initial cost is generally lower than that required with thelaying of electricity power lines, petrol or diesel engines aregenerally more expensive to operate due to fuel costs and areinconvenient with respect to maintenance required, pollution and noise.

3. A windmill is positioned in close proximity to the water pump and thewater source. The disadvantage with this arrangement is that windmillshave poor efficiency in hilly country. The reason for this is that sincea water source is likely to be located in low lying areas the windmillmust also be located in the low lying areas and thus would be shelteredfrom the wind required to operate the windmill.

4. A farm tractor is coupled to the water pump and operated to power thewater pump. The disadvantage with this arrangement is that while thetractor is being used to power the water pump the tractor cannot be usedfor other purposes.

A so-called injector pump has been proposed to avoid the necessity tolocate the water pump in close proximity to the water source. Theinjector pump may be located remote from the water source and connectedto the water source by two conduits. One conduit delivers fluid to aninjector/venturi apparatus at or in the water source and this causesfluid to be drawn into and delivered through the other conduit back tothe pump outlet. The disadvantages with this arrangement are that thereare practical limits with respect to the distance over which injectorpumps will operate efficiently, and the energy input to operate theinjector pump is high and the two conduits are necessarily large indiameter and therefore expensive.

It is an object of the present invention to provide an apparatus forpumping fluids which alleviates the disadvantages of the known apparatusdescribed in the preceding paragraphs.

It is also an object of the invention to provide an improvedhydraulically operated fluid pump which is particularly suited for usein the apparatus of the invention for pumping fuilds.

According to the present invention there is provided an apparatus forpumping fluid from a fluid source to a predetermined location, theapparatus comprising:

(a) an hydraulically operated pump adapted to be positioned in fluidcommunication with the fluid source, the pump having a pump chamber anda means for storing potential energy,

(b) a conduit connectible to the pump and to a supply of hydraulic fluidpositioned remote from the pump,

(c) a control means operatively connectible to said conduit toperiodically allow pulses of hydraulic fluid to be transmitted into saidconduit from said supply of hydraulic fluid to actuate said pump,

whereby in use a portion of the energy of each pulse of hydraulic fluidreceived by the pump is stored as potential energy in said means forstoring potential energy and substantially the remainder of the energyactuates said pump to draw fluid from said source into said pumpchamber, and during the time between successive pulses the potentialenergy stored in said means for storing potential energy actuates saidpump to pump the fluid from the pump chamber to the predeterminedlocation and to return via the conduit a volume of hydraulic fluidsubstantially equal to the volume of the preceding pulse of hydraulicfluid to said supply of hydraulic fluid.

It is preferred that the fluid to be pumped and the hydraulic fluid bewater, and the supply of hydraulic fluid comprises a water storage tankoperably connectible to said conduit. In one arrangement the water flowsthrough the conduit itself to the predetermined location which isadjacent to or forms part of the water storage tank. In an alternativearrangement, a separate water outlet conduit conveys the water from thepump chamber to the predetermined location which is remote from thewater storage tank.

Preferably, the pump chamber comprises a pumping element operable todraw water into the pump chamber and to pump water therefrom to thepredetermined location, and the pump further comprises a work chamberconnectible to the conduit, the work chamber having a work elementmovable from an equilibrium position in response to changes of pressurein the work chamber caused by pulses of water transferred within saidconduit and the work element is operably connected to the pumpingelement and to the means for storing potential energy.

Preferably, the conduit is operably connectible to the pump chamber,whereby between successive pulses, the potential energy in said meansfor storing potential energy actuates said pumping element to pump waterfrom said pumping chamber within the said conduit to said predeterminedlocation.

It is preferred that the conduit is operatively connectible to a pumpingmeans, and the control means comprises valve means which in use operablyconnects the conduit to the water storage tank and to the pumping means,whereby the control means periodically allows pulses of water to bepumped under pressure by the pumping means from the water storage tankwithin the conduit to the work chamber, and during the time betweensuccessive pulses the control means allows flow of water into the waterstorage tank from the pump chamber together with the volume of watersubstantially equal to the volume of the preceding pulse of waterreturning to the water storage tank within the said conduit from thework chamber.

Alternatively, the control means comprises a piston cylinder and pistonarrangement, the piston being connectible to a pumping means operable toreciprocate the piston within the piston cylinder to define waterdelivery and return strokes, the water storage tank being connectible tothe conduit at a location between the piston cylinder and the waterpump, a one-way valve being positioned to permit water to flow from theconduit into the water storage tank when the pressure within the conduitexceeds a predetermined pressure, whereby in use during a first part ofeach delivery stroke of the piston forces water is forced within theconduit to increase the pressure within the work chamber to actuate thepump, the first part of the delivery stroke concluding when the pressurewithin said conduit and the water pump reaches said predeterminedpressure at which point the valve opens and during the remainder of thedelivery stroke, water flows from the piston cylinder into the waterstorage tank, and on the return stroke of the piston water is drawn intothe piston chamber from the work chamber as the work chamber returns tothe equilibrium position and from the pump chamber.

According to the present invention there is also provided a method ofpumping fluid from a water source to a predetermined location, themethod comprising:

(a) positioning an hydraulically operated pump having a pump chamber andmeans for storing potential energy, in fluid communication with thewater source,

(b) periodically transmitting pulses of hydraulic fluid from a supply ofhydraulic fluid positioned remote from the pump within a conduit to thepump to actuate the pump and thereby draw fluid into the pump chamberand to store potential energy in the means for storing potential energy,and

(c) said means for storing potential energy actuating said pump duringthe time between successive pulses to thereby pump the fluid in saidpump chamber to said predetermined location and to return to said supplyof hydraulic fluid via the conduit a volume of hydraulic fluidsubstantially equal to the volume of the preceding pulse of hydraulicfluid.

According to the present invention there is also provided a method ofpumping liquid from a liquid source to a reservoir in a pumping systemsaid system comprising:

a fluid conduit between the reservoir and the source; and

pumping means near the source, said method comprising the steps ofcausing flow of said fluid in the conduit in a direction from saidreservoir to said source to accumulate energy in said pumping means forsubsequent utilization in a pumping operation of the pumping means inwhich flow of the fluid in the conduit is in the direction from thesource to the reservoir.

According to the present invention there is provided a pump for pumpingfluid, said pump comprising:

a pump chamber having a pumping element operable to draw fluid into thepump chamber and to discharge fluid from the pump chamber,

a means for storing potential energy operatively connected to saidpumping element,

a work chamber connectible to a supply of hydraulic fluid, the workchamber having a work element responsive to changes in hydraulic fluidpressure within said work chamber and operatively connected to thepumping element and the means for storing potential energy,

whereby in use an increase in hydraulic fluid pressure within said workchamber actuates said work element to cause, simultaneously, an increasein the potential energy in said means for storing potential energy andactuation of said pumping element to draw fluid into the pump chamber,and a subsequent decrease in hydraulic fluid pressure within said workchamber causes said means for storing potential energy to actuate saidpumping element to discharge the f1uid drawn into the pump chamber.

In one preferred form, the work element comprises a work diaphragm andthe pump element comprises a pump diaphragm, the two diaphragms beingoperatively connected together by a connecting rod, the means forstoring potential energy comprises an energy storage chamber containingcompressed air, the work chamber and the energy storage chamber beingintegrally formed and separated by said work diaphragm, wherebyincreases in hydraulic fluid pressure within said work chamber causesaid work diaphragm to distend from an equilibrium position thereby,simultaneously, reducing the volume of said energy storage chamber andincreasing the pressure of the compressed air therein and distendingsaid pump diaphragm from an equilibrium position to draw fluid into thepump chamber, and subsequent reduction of pressure within said workchamber causes a pressure imbalance between said work chamber and saidenergy storage chamber with the result that the work diaphragm returnsto its equilibrium position, thereby causing the pump diaphragm toreturn to its equilibrium position and discharge the volume of fluiddrawn into the pump chamber.

In another preferred form, the work element comprises a work pistonmovable within the work chamber in response to changes in hydraulicfluid pressure within the work chamber and the pump element comprises apump piston movable within the pump chamber, said work piston and saidpump piston being connected together by an interconnecting rod, the rodhaving a fluid passageway therein arranged to allow a one-way flow offluid from the pump chamber to the work chamber, whereby in use fluiddrawn into the pump chamber is discharged from said pump chamber throughthe fluid passageway and into said work chamber.

Further detailed description of preferred embodiments of the presentinvention will now be provided with reference to the accompanyingdrawings, in which:

FIG. 1a is a schematic view of one embodiment of apparatus for pumpingwater formed in accordance with the present invention;

FIG. 1b is a schematic view of an alternative embodiment of apparatusfor pumping water formed in accordance with the present invention;

FIGS. 2 to 4 are partially sectional/schematic views illustratingdifferent stages in the operation of one embodiment of the pump formedin accordance with the present invention which is particularly suitedfor inclusion in the apparatus shown in FIG. 1a;

FIG. 5a is a sectional view of another embodiment of the pump formed inaccordance with the present invention which is also particularly suitedfor inclusion in the apparatus shown in FIG. 1a;

FIG. 5b is a sectional view of a modified version of the pump shown inFIG. 5a.

FIG. 5c is a sectional view of another embodiment of the pump formed inaccordance with the present invention which is also particulary suitedfor use with the apparatus shown in FIG. 1a.

FIG. 6 is a schematic view of one embodiment of the control means shownin FIG. 1;

FIG. 7 is a schematic view of another embodiment of the control meansshown in FIG. 1.

In FIG. 1a is shown an apparatus 3 for pumping water from a reservoir 5to a water storage tank 7 positioned remote from the reservoir 5.

The apparatus 3 comprises a water pump 9, which acts as a slave pump,positioned in close proximity to the reservoir 5 and in fluidcommunication therewith by means of a suction conduit 11. A one-wayvalve 13 is positioned on the end of the conduit 11 located within thereservoir 5 to prevent flow of water from the water pump 9 into thereservoir 5.

The apparatus 3 further comprises a conduit 15 which connects the waterpump 9 to the water storage tank 7. A pumping means 17, which acts as anactivating pump, is positioned adjacent the water storage tank 7 and isconnected by conduits 21 and 23 to the water storage tank 7 and theconduit 15 respectively. In use, the pumping means draws water from thewater storage tank 7 and pumps the water down the conduit 15 to thewater pump 9.

The apparatus further comprises a control means 19 which is positionedon the conduit 15 to control the flow of water between the water pump 9and the pumping means 17 and between the water pump 9 and the waterstorage tank 7.

In use of the apparatus, the control means 19 operates to periodicallyallow pulses of water to be pumped by the pumping means 17 down conduit15 to the water pump 9. At the same time the control means 19 preventsflow of water into the water storage tank 7. Each pulse of water pumpeddown the conduit 15 increases the pressure within the water pump 9,which actuates the water pump 9 to draw water from the reservoir 5 intoa pump chamber (not shown) in the water pump 9.

During the time between successive pulses the control means 19 operatesto prevent water returning to the pumping means 17 through the conduit15 and to allow water to flow from the water pump 9 through the conduit15 into the water storage tank 7. Operation of the control means 19 inthis instance results in a reduction in pressure within the conduit 15and the water pump 9, which actuates the water pump 9 simultaneously:

(a) to force the volume of water drawn in the pump chamber from thereservoir 5 through the conduit 15 to the water storage tank 7, and

(b) to return the volume of water delivered into the conduit 15 andwater pump 9 by the preceding pulse of water back through the conduitinto the water storage tank 7.

It can be appreciated that with the above arrangement, for each unitvolume of water forced by the pumping means 17 down the conduit 15 thewater pump 9 is actuated to pump two unit volumes of water into thewater storage tank 7.

In the embodiment described in FIG. 1a, the conduit 15 has the dualpurpose of providing a means by which water can be forced into the waterpump 9 to actuate the water pump and also a means by which water drawnfrom the reservoir 5 into the water pump 9 can be delivered to the waterstorage tank 7. In an alternative embodiment of the invention shown inFIG. 1b, a separate conduit 16 is connected to the outlet 39 of the pumpchamber 34 to deliver the water drawn into the water pump from thereservoir 5 to a predetermined location spaced from the water storagetank 7. In this arrangement the water storage tank 7 functions as ameans for storing water to actuate the water pump and the conduit 15acts as hydraulic energy transfer line only.

The water pump 9 may comprise a water pump formed in accordance with thepresent invention. One embodiment of a water pump formed in accordancewith the present invention is shown in FIG. 2.

The water pump 9 in FIG. 2 is shown in its equilibrium position andcomprises an upper chamber 25 and a lower chamber 27. The lower chamber27 comprises a work chamber 29 and a potential energy storage meanswhich is in the form of an energy storage chamber 31 containingcompressed air. The work chamber 29 and the energy storage chamber 31are separated by a working element which is in the form of a workdiaphragm 33. The work chamber 29 is connected to the conduit 15 and theenergy storage chamber 31 is connected to a supply of compressed airwhich may be introduced into the energy storage chamber through a valve(not shown).

The upper chamber 25 comprises a pump chamber 34 having an inlet 35connected by the conduit 11 to the reservoir 5 and an outlet 37connected by the conduit 15 to the water storage tank 7 (not shown). Oneone-way valves 39 are positioned in the inlet 35 and the outlet 37 todirect a one-way flow of water through the pump chamber 34 from thereservoir 5 and subsequently to the water storage tank 7.

The upper chamber 25 further comprises a pumping element which is in theform of a pump diaphragm 43. The pump diaphragm 43 is connected to thework diaphragm 33 by a connecting rod 45. It can be readily appreciatedthat movement of the work diaphragm 33 in response to changes of waterpressure in the work chamber 29 results in consequential movement of thepump diaphragm 43 in the pump chamber 34.

With reference to FIG. 3, when a pulse of water is pumped down theconduit 15, the one-way valve 39 in the water outlet 37 prevents flow ofwater into the pump chamber 34 and thus the water is directed into thework chamber 29. The pulse of water pumped into the conduit 15 increasesthe pressure in the work chamber 29 with the effect that work diaphragm33 distends from the equilibrium position shown in FIG. 2 downwardlyinto the energy storage chamber 31 thereby causing compression of thevolume of compressed air in the energy storage chamber 31. In addition,the downward movement of the work diaphragm 33 causes a consequentialdownward movement of the pump diaphragm 43 in the pump chamber 34. Thisresults in an increase in volume defined by the pump chamber 34 andcauses a suction effect which opens the one-way valve 39 in the inlet 35and draws water through the conduit 11 from the reservoir 5 into thepump chamber 34.

With reference to FIG. 4, when the pulse of water is expended, due tothe operation of the control means 19 (FIG. 1a), there is a pressurereduction in the conduit 15 and the work chamber 29. As a result, theeis a pressure imbalance between the work chamber 29 and the energychamber 31 and to restore equilibrium the compressed air in the energystorage chamber 31 expands and forces the work diaphragm 33 upwardly tothe equilibrium position shown in FIG. 2. There is a consequentialupward movement of the pump diaphragm 43 in the pump chamber 34 whichcloses the one-way valve in the inlet 35 and opens the one-way valve 39in the outlet 37. The combined effect of the upward movement of the workand pump diaphragms 33 and 43 is that water is forced from both the workchamber 29 and the pump chamber 34 into the conduit 15 and subsequentlyinto the water storage tank 7.

In FIG. 5a is shown another embodiment of the water pump formed inaccordance with the present invention. The water pump shown in FIG. 5a,like the water pump shown in FIGS. 2 to 4, is particularly suited foruse with the apparatus for pumping water shown in FIG. 1a.

The water pump 9 shown in FIG. 5a comprises a cylindrical housing 49closed by end plates 51 and 53. The cylindrical housing 49 is dividedinto two chambers 55 and 57 by means of a dividing plate 59. A piston 61is positioned in chamber 55 and separates the chamber into two chambers63 and 65. Chamber 65 defines a work chamber and is connected by aconduit 89 to conduit 15. A piston 67 is positioned in chamber 57 andseparates the chamber into two chambers 69 and 71. Chamber 71 defines apump chamber and is connected to suction conduit 11 and water reservoir5 through an aperture 91 in end plate 51. A one-way valve 93 ispositioned in aperture 91 to prevent back flow of water from chamber 71into the water reservoir 5.

The two pistons 61 and 67 are interconnected by a hollow connecting rod73 which defines a fluid passageway 77 between the chamber 71 definingthe pump chamber and the chamber 65 defining the work chamber. In thisconnection a port 76 is positioned on the rod 73 adjacent piston 61 toenable flow of fluid between chamber 65 and fluid passageway 77. Inaddition, the opposite end of the rod 73 is positioned in an aperture 79in piston 67. The aperture 79 is closed by a one-way valve 81 whichpermits a one-way flow of fluid from the chamber 71 into the fluidpassageway 77.

Chambers 63 and 69 are connected by conduits 83 and 85 to a fluidaccumulator 87. The chambers 63, 69 and fluid accumulator 87 define apotential energy storage means and contain substantially incompressiblefluid.

In use, a pulse of water forced into conduit 15 from the pumping means17 shown in FIG. 1a, results in water being forced through conduit 89into chamber 65 defining the work chamber. The one-way valve 81positioned in the fluid passage-way 77 prevents flow of water into thechamber 71 defining the pump chamber. The increase in the volume ofwater in the chamber 65 defining the work chamber results in an upwardmovement (as shown in FIG. 5a) of the piston 61 and a consequentialupward movement of piston 67. The combined effect is to force fluidwithin the chambers 63 and 69 into the accumulator 87, under pressure,with the effect that there is an increase in potential energy in theaccumulator 87. In addition, the upward movement of the piston 67 causesa suction effect within chamber 71 defining the pump chamber and causeswater to be drawn from water reservoir 5 through conduit 11 into thepump chamber.

When the control means 19 shown in FIG. 1a terminates the flow of waterpumped within conduit 15 and allows water flow into the water storagetank 7 shown in FIG. 1a there is a resultant drop in pressure withinconduit 15 and chamber 65 defining the work chamber. As a consequencethere is a pressure imbalance between respective chambers 63, 65 and 69and 71, and the accumulator 87 forces downward movement (as shown inFIG. 5a) of the pistons 61 and 67 to return to the equilibrium positionshown in FIG. 5a. The downward movement closes valve 93 and opens thevalve 81 in the fluid passageway 77. As can be appreciated from FIG. 5a,the net result is that the volume of water drawn into the chamber 71defining the pump chamber together with the volume increase of water inthe chamber 65 defining the work chamber caused by the preceding pulseof water within conduit 15, is forced through conduit 15 into the waterstorage tank 7 shown in FIG. 1a.

In the embodiment shown in FIG. 5a, the fluid passageway 77 allows waterto flow from the chamber 71 defining the pump chamber to the chamber 65defining the work chamber. In the modified embodiment shown in FIG. 5bthe fluid passageway connects the chambers 63 and 69 forming part of thepotential energy storage means.

With reference to FIG. 5b, the embodiment shown is substantially similarto the embodiment shown in FIG. 5a except for the following details.First the connecting rod 73 is secured to the two pistons 61 and 67 sothat the fluid passageway connects the chambers 63 and 69 forming partof the potential energy storage means. As a result, it is not necessaryto include the conduit 83 connecting the chamber 69 to the fluidaccumulator 87 as shown in FIG. 5a. Second, the conduit 15 is connectedto both the chamber 65 defining the work chamber and to the chamber 71defining the pump chamber. A one-way valve 81 is positioned to allowflow from the pump chamber into the conduit.

In use of the pump, a pulse of water forced into conduit 15 from thepumping means 17 shown in FIG. 1a, results in water being forced intothe chamber 65 defining the work chamber. The one-way valve 81 preventsflow of water through conduit 15 into the chamber 71 defining the pumpchamber.

The overall result is an increase in volume of water into the chamber 65defining the work chamber which causes an upward movement (as shown inFIG. 5b) of the piston 61 and a consequential upward movement of piston67. The combined effect of the movement of the pistons is to force fluidfrom chambers 63 and 69 into the accumulator 87, under pressure, therebyincreasing the potential energy stored in the accumulator. In additionthe upward movement of the piston 67 causes water to be drawn from thewater reservoir 5 through conduit 11 into the chamber 71 defining thepump chamber.

When the control means 19 shown in FIG. 1a terminates the flow of waterpumped within conduit 15 and allows water flow into the water storagetank 7 shown in FIG. 1a, there is a resultant drop in pressure withinconduit 15 and chamber 65 defining the work chamber. As a consequence,there is a pressure imbalance between respective chambers 63,65 and69,71, and the accumulator 87 forces downward movement of the pistons 61and 67 to return to the equilibrium position shown in FIG. 5b. Thedownward movement closes the valve 93 and thus prevents return flow ofwater from the chamber 71 defining the pump chamber into the reservoir5. However, valve 81 opens and the volume of water drawn into the pumpchamber is forced into the conduit 15, and together with the volume ofwater forced into the chamber 65 defining the work chamber during thepreceding pulse, flows through conduit 15 to the water storage tank 7shown in FIG. 1a.

A further embodiment of a water pump formed in accordance with thepresent invention is shown in FIG. 5c. The water pump shown in FIG. 5c,like the water pumps shown in FIGS. 2 to 4, 5a and 5b, is particularlysuited for use with the apparatus for pumping water shown in FIG. 1a.

The water pump 9 shown in FIG. 5c is similar to the water pumps shown inFIGS. 5a and 5b in that it comprises a cylindrical housing 49 closed byend plates 51 and 53. In addition, the cylindrical housing 49 is dividedinto an upper and a lower chamber by a dividing plate 59.

A piston 67 is positioned in the lower chamber and separates the chamberinto two separate chambers 69 and 71. Chamber 71 defines a work chamberand is connected to conduit 15. A piston 61 is positioned in the upperchamber and separates the chamber into two separate chambers 63 and 65.Chamber 65 defines a pump chamber and is connected by means of conduit11 to water reservoir 5. A valve 93 positioned in conduit 11 allows aone-way flow only of water from reservoir 5 through conduit 11 intochamber 65 defining the pump chamber. In addition, a conduit 82 connectsthe chamber 65 to the conduit 15 and valve 81 positioned in the conduit82 allows one-way flow only of water from the chamber 65 defining thepump chamber into conduit 15 and ultimately into the water storage tank7, as shown in FIG. 1a.

The two pistons 61 and 67 are interconnected by a hollow connecting rod73 which defines a fluid passage way 77 between chambers 63 and 69. Ascan be clearly seen in FIG. 5c, a conduit 85 connects the chambers 63and 69 to a fluid accumulator 87, and together the three componentsdefine a potential energy storage means.

The water pump 9 further comprises roller diaphragms 84, 86 and 88positioned as shown in FIG. 5c to effectively seal the separate chamberswithin the upper and lower chambers respectively.

In use of the water pump 9, a pulse of water forced into conduit 15 fromthe pumping means shown in FIG. 1a results in water being forced intochamber 71 defining the work chamber. The one-way valve 81 prevents flowof water through conduits 15 and 82 into the chamber 65 defining thepump chamber. The overall result is an upward movement (as shown in FIG.5c) of the piston 67 with consequential upward movement of the piston 61together with consquential movement of the roller diaphragms 84, 86 and88. The combined effect of the movement of the pistons is to force fluidfrom the chambers 63 and 69 into the accumulator 87, thereby increasingthe potential energy stored in the accumulator 87. In addition, upwardmovement of the piston 61 causes expansion of the chamber 65 definingthe pump chamber with the effect that water is drawn from the reservoir5 into the pump chamber.

When the control means 19 shown in FIG. 1a terminates the flow of waterpumped within conduit 15 and allows water flow into the water storagetank 7 shown in FIG. 1a, there is a resultant drop in pressure withinconduit 15 and chamber 71 defining the work chamber. As a consequence,there is a pressure imbalance within the lower chamber and theaccumulator 87 returns fluid to the chambers 63 and 69 to force thepistons 61 and 67 downwardly to the equilibrium position shown in FIG.5c. The downward movement closes valve 93 in the chamber 65 defining thepump chamber and thus prevents water flow from the pump chamber intoreservoir 5. However, valve 81 opens and the volume of water previouslydrawn into the pump chamber is forced into the conduit 15, and togetherwith the volume of water forced from the chamber 71 defining the workchamber, due to downward movement of piston 67, flows through conduit 15to the water storage tank 7 shown in FIG. 1a.

The principal difference between the water pumps shown in FIGS. 5a and5b and the water pump 9 shown in FIG. 5c, is the use of rollerdiaphragms 84, 86 and 88 to improve the seal between the separatechambers within the upper and lower chambers respectively. One importantconsequence is that the tolerances between the walls of the pistons 61,67 and the inner wall of the cylindrical housing 49 are not as criticalas is the case with arrangements which do not use roller diaphragms.This is a particularly important advantage in situations where the pumpis used for pumping bore water, since mineralisation of working parts inthe pump can reduce the efficiency of the pump. In addition, to improvethe effectiveness of the roller diaphragms it has been found preferableto reverse the position of the work and pump chambers. Thus, it is notedthat the chamber 65 defines the pump chamber, whereas the chamber 71defines the work chamber.

A particular embodiment of the control means 19 shown in FIG. 1a willnow be described with reference to FIG. 6. The control means 19comprises a three-way valve 103 operated by an electric solenoid 105.The control means 19 operates in the following manner:

1. When the solenoid 105 is energised the three-way valve 103 operatesto allow flow of water from the pumping means 17 through conduits 23 and15 into the water pump 9. At the same time, the three-way valve 103prevents flow of water into the water storage tank 7.

2. When the solenoid 105 is de-energized the three-way valve 103operates to allow flow of water from the water pump 9 through conduit 15into the water storage tank 7. At the same time, the three-way valve 103prevents flow of water from the water pump 9 into the pumping means 17.

The control means further comprises electric circuitry 107 forcontrolling the energizing and de-energizing of the solenoid 105 tooperate the three-way valve 103 to periodically allow pulses of waterfrom the pumping means 17 into the water pump 9 and return flow of waterfrom the water pump 9 into the water storage tank 7.

The electronic circuitry operates in the following manner:

1. The electronic circuitry energizes the solenoid 105 for a sufficienttime to allow a preselected volume of water to flow from the pumpingmeans 17 through conduits 23 and 15 to the pumping means.

2. The electronic circuitry then de-energizes the solenoid 105 for asufficient time to allow the water forced from water pump 9 to passthrough the three-way valve 103 to the water storage tank 7.

The embodiment of control means 19 described above is particularlysuitable for use with conventional household "constant pressure" pumpingsystems.

A second embodiment of the control means 19 which is particularly suitedfor use with pumping means 17 in the form of a windmill is shown in FIG.7. The control means 19 comprises a piston cylinder 115 and piston 117.The piston 117 is coupled to a windmill 118 (or any other suitable powermeans) to reciprocate the piston 117 within the cylinder 115. The pistoncylinder 115 is connected at its lower end to conduit 15 and a branchconduit 119 connects the conduit 15 to the water storage tank 7. Aspring loaded valve arrangement 121 is positioned on the conduit 119 toclose the valve and prevent flow of water through the conduit 119 intothe water storage tank 7.

In use, for a part of the water delivery stroke of the piston 117 waterflows within conduit 15 to actuate the water pump 9. The arrangement issuch that the part of the delivery stroke delivers a sufficient volumeof water to fully actuate the work element in the working chamber of thewater pump 9.

During the remainder of the water delivery stroke the increase inpressure within conduit 15 is sufficient to open the spring loaded valvearrangement 121 to allow the volume of water delivered by the remainderof the water delivery stroke to flow through conduit 119 into the waterstorage tank 7.

On the return stroke of the piston 117 the piston cylinder 115 isrecharged by:

(a) the volume of water corresponding to the volume of water deliveredby the first part of the water delivery stroke, and

(b) the additional water drawn into the pump chamber of the water pump 9from the reservoir 5.

It can be readily appreciated that although the present invention hasbeen described in relation to use in agriculture, the invention is notso limited, and could be used in a number of applications, includinggeneral applications in medical and industrial fields.

I claim:
 1. A pumping system for pumping fluid, said system comprising:a pump chamber having a pumping element operable to draw fluid into the pump chamber and to discharge fluid from the pump chamber, means for storing potential energy operatively associated with said pumping element, a work chamber connectible to a supply of hydraulic fluid, the work chamber having a work element responsive to changes in hydraulic fluid pressure within said work chamber and operatively connected to the pumping element and the means for storing potential energy, whereby in use an increase in hydraulic fluid pressure within said work chamber actuates said work element to cause, simultaneously, an increase in the potential energy in said means for storing potential energy and actuation of said pumping element to draw fluid into the pump chamber, and a subsequent decrease in hydraulic fluid pressure within said work chamber causes said means for storing potential energy to actuate said pumping element to discharge the fluid drawn into the pump chamber, wherein the means for storing potential energy comprises a fluid accumulator and first and second potential energy storage chambers; the work element comprises a work piston separating the work chamber from the first potential energy storage chamber, the work piston being movable in response to changes of hydraulic fluid pressure within said work chamber; the pumping element comprises a pump piston separating the pump chamber from the second potential energy storage chamber; an interconnecting rod connecting the work piston and the pump piston together whereby the pump piston is movable in response to movement of the work piston, the interconnecting rod defining a fluid passageway connecting the first and second potential energy chambers.
 2. A pumping system according to claim 1, wherein the fluid accumulator is remote from the first and second potential energy storage chambers and is connected thereto by means of a conduit.
 3. A pumping system comprising an actuating pump, a slave pump having a piston assembly for drawing liquid from a liquid source, a pipeline connecting the actuating pump to the slave pump, and a hydraulic accumulator associated with the slave pump, said actuating pump being operable to supply a volume of liquid along said pipeline to said slave pump in order to drive a piston assembly of said slave pump and to store potential energy in the hydraulic accumulator, the energy stored in said accumulator thereafter releasing in order to drive the piston assembly of the slave pump so as to deliver a volume of liquid greater than that supplied by the actuating pump, wherein the slave pump comprises a cylinder having end walls and an intermediate wall, the piston assembly of the slave pump comprises two pistons and a hollow piston rod interconnecting the pistons for movement within the cylinder, said pistons being on respective sides of the intermediate wall and said pistons defining, with the intermediate and end walls of the cylinder, a work chamber connected to the pipeline to receive the actuating volume of liquid, a pump chamber having inlet means into which liquid is drawn when the interconnected pistons are displaced, means connecting the pump chamber to the pipeline for delivery of the liquid, and first and second accumulator chambers interconnected via the piston rod and connected to the hydraulic accumulator whereby during the delivery stroke, the pressure in the hydraulic accumulator acts on two piston faces of the piston assembly, the first and second accumulator chambers being at opposite sides of the intermediate wall, with the first accumulator chamber being adjacent the intermediate wall and the second accumulator chamber being adjacent the end wall remote from the first accumulator chamber, and the work chamber and the pump chamber being at opposite sides of the intermediate wall and each adjacent a respective one of the two accumulator chambers, one from the work chamber and pump chamber being adjacent the intermediate wall on the side thereof opposite the first accumulator chamber and the other from the work chamber and pump chamber being adjacent the end wall remote from the second accumulator chamber.
 4. A pumping system comprising an actuating pump, a slave pump having a piston assembly for drawing liquid from a liquid source, a pipeline connecting the actuating pump to the slave pump, and a hydraulic accumulator associated with the slave pump, said actuating pump being operable to supply a volume of liquid along said pipeline to said slave pump in order to drive a piston assembly of said slave pump and to store potential energy in the hydraulic accumulator, the energy stored in said accumulator thereafter releasing in order to drive the piston assembly of the slave pump so as to deliver a volume of liquid greater than that supplied by the actuating pump, wherein the slave pump comprises a cylinder having end walls and an intermediate wall, the piston assembly of the slave pump comprises two pistons interconnected for movement within the cylinder, said pistons being on respective sides of the intermediate wall and said pistons defining, with the intermediate and end walls of the cylinder, a work chamber connected to the pipeline to receive the actuating volume of liquid, a pump chamber having inlet means into which liquid is drawn when the interconnected pistons are displaced, means connecting the pump chamber to the pipeline for delivery of the liquid, and first and second interconnected accumulator chambers connected to the hydraulic accumulator whereby during the delivery stroke, the pressure in the hydraulic accumulator acts on two piston faces of the piston assembly, the first and second accumulator chambers being at opposite sides of the intermediate wall, with the first accumulator chamber being adjacent the intermediate wall and the second accumulator chamber being adjacent the end wall remote from the first accumulator chamber, and the work chamber and the pump chamber being at opposite sides of the intermediate wall and each adjacent a respective one of the two accumulator chambers, one from the work chamber and pump chamber being adjacent the intermediate wall on the side thereof opposite the first accumulator chamber and the other from the work chamber and pump chamber being adjacent the end wall remote from the second accumulator chamber, said accumulator being remote from the slave pump, and a conduit connecting the said two accumulator chambers to the accumulator. 